1. Field of the Invention
The present invention generally relates to an apparatus and a method for inspecting patterns formed on a wafer. More particularly, the present invention generally relates to an apparatus and a method for inspecting dies on a semiconductor wafer to determine the position of pattern defects.
A claim of priority is made to Korean Patent Application No. 2003-86368, filed on Dec. 1, 2003 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
2. Description of the Related Art
A conventional semiconductor wafer includes a plurality of dies where integrated circuit devices are printed thereon. The integrated circuit device is fabricated by complex processes, including a series of inspection steps performed on patterns formed on the integrated circuit device. A complete inspection is typically performed to verify the accuracy of the patterns formed on the wafer. One conventional inspection method is a die-to-die method. The die-to-die method is a method where a sample die is compared with its adjacent dies.
The conventional die-to-die method will now be described with reference to FIG. 1.
As shown in FIG. 1, a conventional wafer has a plurality of two-dimensionally partitioned dies. In the die-to-die method, a sample die 1 is inspected by comparing the patterns formed on die 1 with the patterns formed on adjacent dies 2 and 3.
In the case where a die 4 is disposed at an edge of a wafer, adjacent dies 5 and die 6 are selected as reference dies, because there is only one immediate adjacent die 5. Here, die 4 is a non-functional die, because it is an incomplete die. If a pattern at a specific position on sample die 4 is identical to at least one of reference dies 5, 6, that position is determined as defect-free, i.e., normal.
In another scenario, if a similar defect occurs at the same position on both reference dies, the sample die will be deemed defective even if that position on the sample die is normal. Furthermore, in the case where the sample die and one of the reference dies are similarly defective at the same position, the pattern corresponding to this position on the sample die will be deemed normal. As described above, die 4 disposed at the wafer edge is non-functional. When die 5 is inspected, because die 4 is incomplete and non-functional, and if die 6 is defective, die 5 will be deemed as defective even though it is normal.
The die-to-die method is inaccurate; therefore, a better inspection method is required.